The software maker urged the more than 1 billion users of Flash on Windows, Mac, Chrome and Linux computers to update the product as quickly as possible after security researchers said the bug was being exploited in "drive-by" attacks that infect computers with ransomware when tainted websites are visited.
Ransomware encrypts data, locking up computers, then demands payments that often range from 0 to 0 to unlock each infected PC.
Such bugs, known as "zero days," are highly prized because they are harder to defend against since software makers and security firms have not had time to figure out ways to block them.
The company released an emergency security bulletin on Tuesday that addresses vulnerabilities in Flash, which could be exploited by hackers.
"This vulnerability could allow an attacker to remotely take control of the affected system," Adobe wrote in a blog post.
Japanese security software maker Trend Micro Inc said that it had warned Adobe that it had seen attackers exploiting the flaw to infect computers with a type of ransomware known as 'Cerber' as early as March 31.
Cerber "has a 'voice' tactic that reads aloud the ransom note to create a sense of urgency and stir users to pay," Trend Micro said on its blog.